Severe haze in northern China: A synergy of anthropogenic emissions and atmospheric processes

Abstract

Regional severe haze represents an enormous environmental problem in China, influencing air quality, human health, ecosystem, weather, and climate. These extremes are characterized by exceedingly high concentrations of fine particulate matter (smaller than 2.5 µm, or PM2.5) and occur with extensive temporal (on a daily, weekly, to monthly timescale) and spatial (over a million square kilometers) coverage. Although significant advances have been made in field measurements, model simulations, and laboratory experiments for fine PM over recent years, the causes for severe haze formation have not yet to be systematically/comprehensively evaluated. This review provides a synthetic synopsis of recent advances in understanding the fundamental mechanisms of severe haze formation in northern China, focusing on emission sources, chemical formation and transformation, and meteorological and climatic conditions. In particular, we highlight the synergetic effects from the interactions between anthropogenic emissions and atmospheric processes. Current challenges and future research directions to improve the understanding of severe haze pollution as well as plausible regulatory implications on a scientific basis are also discussed.

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIRCPC)

“…Hence, the present review paper provides a synopsis of the new findings in those papers, centering on CAPI. The chemical formation and transformation of haze pollution, as well as the influence from emissions and meteorological conditions in East Asia, have recently been reviewed systematically by others (e.g., An et al, 2019;, so the present work is an important complement to them. This paper is structured as follows: section 2 summarizes the major methodologies employed in the papers of the current special issue, including groundbased, airborne, and spaceborne observations, as well as numerical models; section 3 reviews the studies pertaining to aerosol physicochemical properties; section 4 discusses the research about process-level understanding of aerosol effects on cloud and precipitation properties; section 5 reviews the large-scale effects of aerosols on the regional climate over East Asia; and section 6 summarizes the new findings in the current special issue and future challenges and directions.…”

Estimation of Secondary Organic Aerosol Formation During a Photochemical Smog Episode in Shanghai, China

“…Although great strides have been made in the past decades, the estimation of SOA in the atmosphere is still highly uncertain (An et al, 2019; Ehn et al, 2014; Kanakidou et al, 2005; Shrivastava et al, 2017; Volkamer et al, 2006). It remains difficult to quantify the contribution of precursors in the ambient environment.…”

Initial Cost Barrier of Ammonia Control in Central China

“…Ammonia emission control has received a lot of attention especially for controlling the severe haze pollution in China. Recently, An et al (2019) indicated a 50% reduction in ammonia yielded a 10% reduction in PM 2.5 in a haze event in North China. NO 3 − will be further enhanced if ammonia emissions are not reduced, and the reduction in ammonia emissions is beneficial to PM 2.5 control for most regions .…”

“…NO 3 − will be further enhanced if ammonia emissions are not reduced, and the reduction in ammonia emissions is beneficial to PM 2.5 control for most regions . Recently, An et al (2019) indicated a 50% reduction in ammonia yielded a 10% reduction in PM 2.5 in a haze event in North China. Liu et al (2019) also implied that a 50% reduction in ammonia emissions with a 15% reduction in sulfur dioxide and nitrogen oxides can reduce PM 2.5 by 11% − 17%.…”